This project is based on the hypothesis that neural mechanisms in the control of respiration are more important than traditionally believed. The studies use the neural output, represented by phrenic or other nerve activity, of the respiratory control system rather than ventilation, allowing use of "open-loop" experimental conditions. The input-output characteristics of the control system to neural stimuli are being studied. In particular, the studies are looking at 1) ability of the central neural system to maintain its own activity by a reverberatory mechanism is being studied; 2) alinearity in the conversion of input signals to output; 3) the function of the intermediate area (Is) of the ventral surface of the medulla in the processing of central chemoreceptor, carotid body and muscle afferents.